Pump shaft with fastening bolts

ABSTRACT

A retaining device for an impeller of a centrifugal pump, including: a pump shaft with a recess formed substantially parallel to the axis of rotation of the pump shaft; a fastening bolt, which is insertable into the recess such that a first channel is defined between the inserted fastening bolt and the pump shaft and which is connected to the pump shaft on one end thereof and provides a retainer for fixing the impeller on the other end thereof; wherein the pump shaft includes at least one further channel extending from the circumferential surface of the pump shaft up to and into the recess and allowing the first channel to be emptied.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to German Patent Application No.20 2019 105 336.4 filed on Sep. 26, 2019. The entire contents of theabove-listed application are hereby incorporated by reference for allpurposes.

TECHNICAL FIELD

The present invention relates to a retaining device for an impeller of acentrifugal pump.

BACKGROUND

Driving a centrifugal pump via a suitable, powerful motor is known inthe prior art. The centrifugal pump typically has an impeller withblades or vanes, which drive the medium to be pumped. The drive work ofthe motor is converted into kinetic energy of the medium. In order totransmit the driving force of the motor to the centrifugal pump, themotor is provided with a motor shaft. This shaft often has a stub-likedesign. The centrifugal pump, in turn, has a pump shaft as the unit thattransmits the driving force of the motor between the motor shaft and thepump impeller. The pump shaft is typically configured as a hollow shafton the motor side. It is connected to the motor shaft on one end thereofand to the pump impeller on the other end thereof. The pump shaft isusually connected to the motor shaft via a press-fit or shrink-fitconnection, so as to transmit the forces in question and ensure highconcentricity.

In known pumps, the impeller is usually attached to the pump shaft fromthe front and secured against rotation through form-fit geometry. Axialfixing of the impeller takes place by screw fastening via a central nut,which is screwed onto a threaded stud provided on the end of the pumpshaft. This threaded stud is usually formed directly on the pump shaftby means of turning and thus normally has a very short clamping length,which, in practice, may cause the pump nut and the impeller to disengageif vibrations occur. This usually results in destruction of the pump.

For pumps used in the food industry, it is indispensable that all pointsof separation formed in the product area between the individualcomponents are sealed hygienically. This applies in particular to thepoints of separation between the pump impeller and the pump nut andbetween the pump impeller and the rotating part of the mechanical seal.In addition, especially for pumps with a mechanical seal capable ofbeing cleaned with a liquid, a third seal may be placed between themechanical seal and the pump shaft.

These seals create a cavity between the pump shaft and the impellerwhich is not ventilated. Such dead spaces may cause sterility or hygieneproblems in the pumps used, e.g. when the latter are used in the foodindustry. Especially if a sealing element becomes leaky, there may be aningress of leakage into this space, which cannot be removed by normalcleaning and cannot be detected from the outside.

Taking into account these problems, it is the object of the presentinvention to provide a pump shaft for a centrifugal pump, in the case ofwhich the above-described sterility or hygiene problems are reduced ordo not occur at all.

SUMMARY

Disclosed is a retaining device for an impeller of a centrifugal pump,comprising a pump shaft with an opening formed substantially parallel tothe axis of rotation of the pump shaft; a fastening bolt, which isinsertable into the opening and may be adapted to be screw-fastened onthe end of the latter, so that a channel is defined between the insertedbolt and the pump shaft; wherein the pump shaft comprises on at leastone end of the opening at least one channel extending from thecircumferential surface of the pump shaft up to and into the opening andallowing the channel to be emptied.

The terms opening and recess are to be understood as synonyms when usedherein.

The fastening bolt is advantageously at the end of the central bore andmay be screw-fastened to the pump shaft, so that the at least oneadditional channel, which vents the central channel, ends into the pumplantern between the pump casing and the motor, thus allowing detectionof a leakage and venting of the space between the pump impeller and thepump shaft.

Due to the depth of the bore, an increased length of the fastening boltis obtained, which, in turn, substantially extends the clamping lengthin comparison with a threaded stud formed by turning and thus increasesthe safety against loosening of the impeller nut. The fastening bolt mayadvantageously be configured as a waisted stud bolt with rolled threads.

In some aspects, the retaining device the fastening bolt may be threadedand bracing may take place by screwing.

In other aspects, the retaining device, the fastening bolt may beinsertable into and removable from the opening from at least one end ofthe pump shaft.

Additionally provided herein is a centrifugal pump for use in plants forproducing foodstuff, cosmetics and pharmaceutical products, comprising:a pump casing; an impeller with impeller blades for feeding a medium inthe pump casing; and a retaining device of the type describedhereinbefore.

In the centrifugal pump the channel in the pump shaft may, in theretaining device, be longer than the thickness of the impeller and ofthe one or the plurality of mechanical seals, measured along the axis ofrotation of the pump shaft.

In the centrifugal pump, the retaining device with the pump shaft may,in the area in which the pump casing overlaps the pump shaft, compriseone or a plurality of channels produced by boring and extending from thecircumferential surface of the pump shaft up to the central bore, saidchannels allowing access to the channel in the area of the pump casing.

In the centrifugal pump, mechanical seals may be used for sealing thepump shaft against the pump casing.

The mechanical seal may seal the pump shaft against the pump casing in asuitable manner.

In the centrifugal pump, the transverse bores may allow communicationbetween the channel and the area behind the mechanical seals. In thisway, this area can be vented and emptied.

The mechanical seals may be flushable or rinsable, e.g. they may becapable of being cleaned by flushing the bearing, typically using somefluid.

In the centrifugal pump, the pump casing and/or the impeller may bereplaceable.

In the centrifugal pump, the pump shaft may be connectable to a motorshaft. The pump shaft may be adapted to be braced onto the motor shaftby means of a clamping element.

Further provided is an apparatus in the field of foodstuff and drink andtobacco handling, such as a bottling plant or a tank storage, theapparatus comprising one or a plurality of the centrifugal pumps of thetype described hereinbefore.

BRIEF DESCRIPTION OF THE FIGURES

In the following, embodiments of the present invention will be describedmaking reference to the figures. The embodiments described are to beregarded as being merely illustrative in all respects and as beingnon-limiting, and various combinations of the features disclosed arecomprised in the present invention.

FIG. 1A: a schematic view of a centrifugal pump according to anembodiment.

FIG. 1B: a schematic side view of the centrifugal pump according to FIG.1A.

FIG. 2: a schematic side view of a detail of a known centrifugal pump.

FIG. 3: a schematic view of a detail of FIG. 1B concerning the pumpshaft according to an embodiment.

FIG. 4 a schematic view of a pump with a retaining device according toan embodiment, the embodiment in question having two mechanical sealsand the possibility of cleaning the interior of the mechanical seals byflushing them with a liquid.

DETAILED DESCRIPTION

FIGS. 1-4 show example configurations with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such, in at least one example. Asyet another example, elements shown above/below one another, at oppositesides to one another, or to the left/right of one another may bereferred to as such, relative to one another. Further, as shown in thefigures, a topmost element or point of element may be referred to as a“top” of the component and a bottommost element or point of the elementmay be referred to as a “bottom” of the component, in at least oneexample. As used herein, top/bottom, upper/lower, above/below, may berelative to a vertical axis of the figures and used to describepositioning of elements of the figures relative to one another. As such,elements shown above other elements are positioned vertically above theother elements, in one example. As yet another example, shapes of theelements depicted within the figures may be referred to as having thoseshapes (e.g., such as being circular, straight, planar, curved, rounded,chamfered, angled, or the like). Further, elements shown intersectingone another may be referred to as intersecting elements or intersectingone another, in at least one example. Further still, an element shownwithin another element or shown outside of another element may bereferred as such, in one example. It will be appreciated that one ormore components referred to as being “substantially similar and/oridentical” differ from one another according to manufacturing tolerances(e.g., within 1-5% deviation).

FIG. 1A shows a schematic view of a centrifugal pump 100. Thecentrifugal pump 100 comprises a motor 101 with a motor housing 102. Themotor may be mounted on or with a base 103. The motor of the centrifugalpump may drive a motor shaft 1. The motor shaft 1 may be connectable toa pump shaft 2. The pump shaft 2 is connected to an impeller 5. The pumpblades of the impeller 5 are not shown in FIG. 1A. In FIG. 1A, the motorshaft 1 and the pump shaft 2 are connected to each other. For theconnection, the pump shaft 2 is configured as a hollow shaft at one endthereof. In addition, the motor shaft is configured as a stub shaft. Thepump shaft 2 is pushed over the stub shaft of the motor shaft 1. To thisend, the stub shaft of the motor shaft 1 and the pump shaft 2 areconfigured such that the pump shaft 2 surrounds the stub shaft of themotor shaft 1. An overlap area is formed. Over at least part of theoverlap area between the pump shaft 2 and the motor shaft 1, a clampingelement 3 may be provided (see FIG. 3). The clamping element 3 and thepump shaft 2 typically form a unit. The clamping element encompasses thepump shaft 2 and thus the motor shaft 1. The clamping element 3 createsa very large non-slip connection surface between the motor shaft 1 andthe pump shaft 2, thus providing a stable, high concentricity of thepump shaft 2.

FIG. 1B shows a side view of the centrifugal pump 100 of FIG. 1A. On theright hand side of this FIG. 1B, the motor 101 is shown, at the centerof the figure the motor shaft 1 and on the left hand side of the figurethe pump shaft 2. In the area of the pump shaft 2, in particular of theimpeller 5, an area Z is highlighted. This area Z is shown enlarged inFIG. 3.

FIG. 2 shows a detail Z′ of a known centrifugal pump 200. The detail Z′in a known centrifugal pump corresponds approximately to the location ofdetail Z of FIG. 1B. FIG. 2 shows a pump shaft 202 having a pumpimpeller 205 with blades 211 attached thereto. The pump shaft 202 wouldcontinue to the right and may then be connected to a motor shaft, whichis not shown here. The detail Z′ also shows a pump casing 204. FIG. 2shows seals 215. The seals 215.1, 215.3 seal the parts mounted on thepump shaft, viz. the impeller 205 and the impeller nut 206, against theproduct area 225, and the seal 215.2 seals the movable part of themechanical seal against the pump shaft. The seal 215.2 is in particularrequired for pumps having a mechanical seal capable of being cleaned byflushing with a liquid. The area 225 close to the product in questionmay also be referred to as product side or end side or suction side. Ina purely illustrative area 201, which is drawn by dashed lines withoutregard to actual size ratios, a dead space may be formed between thepump shaft 202, the pump impeller 205 and the impeller nut 206. Thisdead space is very difficult to access in the known centrifugal pump 200and therefore very difficult or impossible to clean in case of ingressof leakage. In addition, leakage occurring in this area cannot bedetected from the outside. Furthermore, in this dead space there is therisk that pressure may build up when the temperature changes, and thispressure may return leakages, back into the product and thus lead torecontamination of further product batches.

FIG. 3 shows the area Z of FIG. 1B in an enlarged representation. FIG. 3with the area Z shown is comparable to FIG. 2 and the area Z′ shownthere. FIG. 3 essentially shows a pump shaft 2. In addition, it showsthe pump shaft 2 in relation to a pump casing/pump cover 4, in which theimpeller 5 of the centrifugal pump 100 rotates. The impeller 5 may havea number of blades or delivery elements 5.1. The pump shaft 2 isconnected to the motor shaft 1. The pump shaft 2 is configured as ahollow shaft. The hollow end, shown here in the drawing on the right andidentified by reference numeral 2.1, accommodates the stub shaft of themotor shaft 2. The impeller 5 is driven by the pump shaft 2 connected tothe motor shaft 1. The pump shaft 2 is braced onto the motor shaft 2 bymeans of the clamping element 3.

FIG. 1B already indicates and FIG. 3 shows in detail that the pump shaft2 is hollow and has a bolt or rod 17 inside. This bolt may be afastening bolt. The bolt 17 is oriented along the axis of rotation ofthe pump shaft 2 and cylinder-symmetric thereto. The bolt 17 comprisestwo ends, 17.1 and 17.2. One of the ends of the bolt, in the drawing theend 17.2, faces the motor 101, the other one, in the drawing the end17.1, faces away from the motor 101. The end 17.2 of the bolt is held bya retainer 23 in the motor-side end of the pump shaft bore. The end 17.1may protrude beyond the pump shaft 2 and receives, by means of aretainer 21, the impeller nut 7 thereon, thus fixing the pump impeller 5on the pump shaft. In particular, the fastening bolt 17 may beconfigured as a threaded bolt and the retainers 21 and 23, respectively,may have threads for retaining the bolt 17 by means of the thread. Thefastening bolt 17 is thus oriented along the pump shaft 2 so that thecenter axis of the fastening bolt 17 and of the pump shaft 2 coincide.

In FIG. 3, it is additionally shown that the fastening bolt 17 extendsin a channel 18. The channel 18 is a venting channel. The ventingchannel 18 has a slightly larger diameter than the fastening bolt 17 andis otherwise formed essentially concentrically around the fastening bolt17. Similar to FIG. 2, the area 201 is also indicated in this case,again in a purely illustrative manner and not to scale. In the area 201,internal sealing elements, such as the seals 15.1, 15.2 and 15.3, areindicated. In contrast to FIG. 2, the venting channel 18 in FIG. 3 nowallows access to the area 201, i.e. to the space that was practicallyinaccessible in FIG. 2. Hence, the venting channel 18 creates betweenthe pump shaft 2 and the fastening bolt 17 a gap, which makes the area201 accessible. This gap, i.e. the venting channel 18, can be used todischarge leakage in the event of a partial failure of a sealingelement. The leakage can here enter the venting channel 18 on the endside or via one or a plurality of additional channels. Such additionalchannels are identified by reference numerals 19.2 and 19.3 in FIG. 3.Furthermore, in the bottom of the pump shaft 2, another channel isshown, which is identified by reference numeral 19.1 and through whichleakage can exit in the area of the lantern between the pump casing andthe motor.

In other words, FIG. 3 shows a centrifugal pump 100 and a pump shaft 2for this centrifugal pump 100 with a recess in the pump shaft 2 formedsubstantially parallel to the axis of rotation of the pump shaft 2. Thepump shaft 2 has provided therein a fastening bolt 17. This fasteningbolt 17 can be inserted into the recess, so that a channel 18 will beformed between the fastening bolt 17 and the pump shaft 2, when thefastening bolt has been inserted into the bore. This means that, atleast in an area of the recess, the channel 18 is equal to a ventinggap, when the fastening bolt 17 has been inserted into the bore. Thefastening bolt 17 is braced with the pump shaft 2 at one end of the pumpshaft making use of a respective retainer 23. At least one channel 19.1is provided in the pump shaft 2 at at least one end of the recess, thechannel starting on the circumferential surface of the pump shaft 2.This channel 19.1 extends up to and into the venting channel 18, so thatthe channel 18 can be emptied.

The long clamping length of the threaded connection between the pumpshaft 2 and the impeller nut 7 via the fastening bolt 17 increases thesafety against loosening of the impeller nut 7 and thus of the impeller5 from the pump shaft 2. In addition, the leakage channels/ventingchannels 18 and 19.1, 19.2, 19.3 allow detection of a defect of theinternal sealing elements 15.1, 15.2 and 15.3. By venting the interiorin the area 201, a pressure build-up in this area is prevented and thusthe risk of recontamination in the event of failure of a seal isminimized.

FIG. 4 shows a detail, comparable to detail Z in FIG. 3, of a pumpprovided with the retaining device described, but in a version with twomechanical seals 8, 9. Where identical elements are identified, FIG. 4uses the same reference numerals as FIG. 3. The two mechanical seals 8and 9 may be alike. Furthermore, there is the possibility of cleaningthe inside of the mechanical seals by flushing them with a liquid. Forthis purpose, a flushing channel 403 is indicated in the figure. In FIG.4 it can also be seen that the venting channel 18 penetrates the pumpimpeller 5 and both mechanical seals 8, 9 along the longitudinal axisand is then vented to the outside via the channel 19.1 and through adriver 401.

1. A retaining device for an impeller of a centrifugal pump, comprising:a pump shaft with an opening formed substantially parallel to an axis ofrotation of the pump shaft; a fastening bolt insertable into the openingsuch that a channel is defined between the inserted fastening bolt andthe opening of the pump shaft, wherein the fastening bolt is connectedto the pump shaft on one end thereof and provides a retainer for fixingthe impeller on an other end thereof, wherein the pump shaft comprisesat least one further channel extending from a circumferential surface ofthe pump shaft up to and into a recess and allowing the channel definedbetween the inserted fastening bolt and the opening of the pump shaft tobe emptied.
 2. The retaining device according to claim 1, wherein thefastening bolt is a threaded bolt having a thread on at least one of itsends.
 3. The retaining device according to claim 1, wherein the retaineris provided with a thread and bracing is accomplished by screwing. 4.The retaining device according to claim 1, wherein the fastening bolt isinsertable into and removable from a bore from at least one end of thepump shaft.
 5. The retaining device according to claim 1, wherein theopening formed substantially parallel to the axis of rotation of thepump shaft extends through a length of the pump shaft.
 6. The retainingdevice according to claim 1, wherein the opening formed substantiallyparallel to the axis of rotation of the pump shaft does not extendthrough a length of the pump shaft.
 7. A centrifugal pump for use inplants for producing foodstuff, cosmetics and pharmaceutical products,comprising: a pump casing; an impeller with impeller blades for feedinga medium in the pump casing; and a retaining device comprising: a pumpshaft with an opening formed substantially parallel to an axis ofrotation of the pump shaft; a fastening bolt insertable into the openingsuch that a channel is defined between the inserted fastening bolt andthe opening of the pump shaft, wherein the fastening bolt is connectedto the pump shaft on one end thereof and provides a retainer for fixingthe impeller on an other end thereof, and wherein the pump shaftcomprises at least one further channel extending from a circumferentialsurface of the pump shaft up to and into a recess and allowing thechannel defined between the inserted fastening bolt and the opening ofthe pump shaft to be emptied.
 8. The centrifugal pump according to claim7, wherein, measured along the axis of rotation of the pump shaft, thechannel in the pump shaft is longer than a thickness of the impeller andof an area which one or a plurality of mechanical seals on the pumpshaft overlap.
 9. The centrifugal pump according to claim 7, furthercomprising one or a plurality of mechanical seals for sealing the pumpshaft against the pump casing.
 10. The centrifugal pump according toclaim 9, wherein an area between the plurality of mechanical seals isconfigured to be rinsed.
 11. The centrifugal pump according to claim 7,wherein the pump shaft is provided with one or a plurality of channelsin an area in which the pump casing overlaps the pump shaft, thechannels extending from the circumferential surface of the pump shaft upto the opening, which is formed substantially parallel to the axis ofrotation of the pump shaft, and allowing access to the channel definedbetween the inserted fastening bolt and the opening of the pump shaft.12. The centrifugal pump according to claim 11, wherein the plurality ofchannels in the area in which the pump casing overlaps the pump shaftallow communication between the channel defined between the insertedfastening bolt and the opening of the pump shaft and an area behind theinternal sealing elements.
 13. The centrifugal pump according to claim7, wherein the pump casing and/or the impeller are replaceable.
 14. Thecentrifugal pump according claim 7, wherein the pump shaft isconnectable to a motor shaft.
 15. The centrifugal pump according toclaim 7, wherein the pump shaft is adapted to be braced onto a motorshaft via a clamping element.